This invention relates to a heat-sensitive recording apparatus in which a thermal head records data on a recording sheet.
For instance, in a heat-sensitive recording apparatus using an ink donor film, the thermal head is brought into contact with the ink donor film and the heat generating units of the thermal head are selectively heated according to video data to be recorded. More specifically, thermally sensitive ink coated on the ink donor film is molten according to the video data, and the ink thus molten is transferred onto the recording sheet, so that the video data are recorded on the sheet. In such a thermal transfer type heat-sensitive recording apparatus, it is necessary to press the sheet through the ink donor film against the thermal head under a predetermined pressure.
FIG. 1 illustrates the recording section of a conventional thermal transfer type heat-sensitive recording apparatus.
As shown in FIG. 1, an ink donor film 1 and a sheet 2 piled one on another are conveyed to the contact region 5 between a thermal head 3 and a back roll 4. The back roll 4 is rotatably mounted on the free end portion of a back roll mounting arm 6 with the aid of a spring 7. During normal operation, the back roll mounting arm 6 is positioned as shown in FIG. 1, and the back roll is pressed against the thermal head by means of the spring 7. The back roll 4 is rotated in the direction of the arrow by a drive roller 8 which is in contact with the back roll 4. The ink donor film 1 and the sheet 2 pass through the contact region 5 while being pressed against the heat generating elements of the thermal head 3. After recording, the ink donor film 1 and the sheet 2 piled one on another are delivered together to the contact region (or nipping region) 9 between the back roll 4 and the drive roll 8. The direction of advancement of the ink donor film 1 is then changed abruptly to the direction of the arrow A at the contact region 9, and simultaneously the sheet 2 is peeled off the film 1. The sheet 2 thus peeled off is moved in the direction of the arrow B and it is finally placed in a paper tray (not shown).
In such a heat-sensitive recording apparatus, the pressure of the ink donor film 1 and the sheet 2 against the thermal head 3 is controlled by the spring 7. Therefore, the recording apparatus suffers from a drawback that the contact pressure between the back roll 4 and the drive roll 8 is changed whenever the spring 7 is adjusted, and accordingly the ink donor film 1 and the sheet cannot satisfactorily or smoothly pass through the contact region 9 without readjusting the contact pressure. If one adjustment is performed, then the other adjustment must also be performed. Therefore, only a skilled person can achieve the adjustment properly.